1. Field of the Invention
This invention relates to the protection of control devices and mechanisms such as servo valves from contaminated operating fluid and more particularly, to a dual filter isolation block for positioning between a source of operating fluid such as hydraulic fluid or oil and the user mechanism or device receiving the operating fluid, wherein the dual filter isolation block includes a main body having a pair of fluid paths, a pair of filters provided in the fluid paths, respectively, and a pair of spools disposed for sliding operation in the main body of the isolation block and intersecting the fluid paths, respectively, such that the operating fluid is selectively diverted through one of the fluid paths and the associated filter, while the remaining fluid path and filter remain free of operating fluid. The latter filter can then be removed and replaced without interrupting operation of the user device because of the constant flow of operating fluid through the first fluid path and filter to the user device.
In a specific embodiment the dual filter isolation block of this invention is designed to isolate hydraulic oil or fluid flowing between an actuator and a servo valve, which actuator operates steam valves on a turbine and the servo valve serves to control operation of the actuator. A pair of distinct fluid paths are provided in the main body of the isolation block to selectively receive operating hydraulic oil or fluid flowing under pressure from a storage tank through the actuator and the isolation block, into the servo valve. Each of these fluid paths includes a removable filter and a pair of spool valves operate in sliding concert in the isolation block and intersect the respective fluid paths, such that the hydraulic operating oil or fluid can be directed from a tank through the actuator and through a selected one of the fluid paths and filters into the servo valve and back from the servo valve through the isolation block and the actuator to the tank, while the other filter is removed and replaced. This operation eliminates the necessity for discontinuing or disrupting operation of the servo valve while typically removing a conventional filter which serves the conventional single fluid path between the actuator and the servo valve.
2. Description of the Prior Art
Various mechanisms are known in the art for diverting fluid flow from one point to another in various types of devices. U.S. Pat. No. 3,521,673, dated Jul. 28, 1970, to Gruner, et al, details a constant flow fluid diverting valve which has six fluid ports and is used in four pipe temperature conditioning systems, with a cylindrical plunger longitudinally movable in a valve body to selectively connect to the appropriate ports. U.S. Pat. No. 4,271,020, dated Jun. 2, 1981, to Van Meter, details a valve for a filter device, wherein the valve assembly includes a rotatable valve spindle removable with respect to a valve housing and having first and second channels communicating with the filter. A bypass channel is also provided to bypass the fluid filter. Fluid may flow through the respective channels, including the bypass channel, responsive to rotation of the spindle into a selected position. U.S. Pat. No. 4,469,131, dated Sep. 4, 1984, to Paul L. Traylor, details a spool valve including a valve stem mounting a pair of valve heads removable in a body and cooperating with various valve seats to direct fluid along respective paths through the fluid body. U.S. Pat. No. 4,501,295, dated Feb. 26, 1985, to Williams, details a transfer valve having a valve casing with a closed bottom, a closed top and a separator plate dividing the interior of the valve casing into an upper chamber and a lower chamber. Inlet and outlet ports communicate with the upper and lower chambers and two additional ports open into both the upper chamber and the lower chamber. Valves are provided in the upper and lower chamber and a control rod extends through the device to simultaneously rotate the valve and channel fluid through the respective ports. U.S. Pat. No. 4,683,914, dated Aug. 4, 1987, to Brisland, details a slide valve having a valve body with a slide mounted therein for controlling opening interconnection and closing of various valve ports in the body. U.S. Pat. No. 5,152,320, dated Oct. 6, 1992, to Zimmerly, details a diverter valve which includes a valve body with two identical sections having valve seats and a valve stem extending through the valve body. A valve actuator lifts the valve stem, closing a pair of plugs in the valves and selectively allowing fluid to flow from various ports communicating with the valve body. U.S. Pat. No. 5,184,643, dated Feb. 9, 1993, to Raymond, details a valve sleeve assembly, typically having a valve sleeve defining a generally truncated, triangular, upraised land formed by complimentary shaped, adjacent recesses, when the sleeve is used as shown in a section taken along a radial plane perpendicular to the axis of the spool bore.
It is an object of this invention to provide a new and improved dual filter isolation block or selectively filtering an operating fluid from a source to a user apparatus or device and facilitating removal and replacement of one of the filters in the isolation block without discontinuing or interrupting operation of the user device.
Another object of the invention is to provide a dual filter isolation block for sandwiching between a source of operating fluid and a user or control device receiving that fluid, which isolation block includes a pair of distinct fluid paths extending through the isolation block and serving a pair of filters, respectively, with a pair of spools operating in sliding concert in the isolation block and extending through the fluid paths, respectively, such that the operating fluid can be selectively diverted through one of the fluid paths and its corresponding filter into the user or control device, thus leaving the second fluid path and filter free of operating fluid to facilitate changing the second filter without the necessity of interrupting the flow of operating fluid from the source to the user or control device.
Still another object of the invention is to provide a dual filter isolation block and method of use for protecting a user device or mechanism from contaminants in operating oil or fluid flowing from a source, which dual filter isolation block is inserted between the source and the user device. The dual filter isolation block is characterized by a pair of fluid paths, each fitted with a filter and a pair of slidably disposed spools intersecting the respective fluid paths to facilitate selective isolation of one of the fluid paths and the filter from the other fluid path and filter by slidable operation of the spools in the isolation block.
Yet another object of this invention is to provide dual filter isolation block and method for isolating an operating oil or fluid such as hydraulic fluid between an actuator and a control device such as a servo valve in order to protect the servo valve from contaminants in the hydraulic fluid. The isolation block includes a main body; a pair of separate fluid paths provided in the main body extending from the actuator to the servo valve and a pair of filters provided in the fluid paths, respectively; and a pair of spools having areas of reduced diameter for fluid flow, the spools slidably disposed in the main body of the isolation block and intersecting the respective fluid paths, such that the flow of hydraulic fluid from the actuator into the servo valve is isolated in and directed through a selected one of the fluid paths, the areas of reduced diameter in the spools and the associated filter and the opposite filter can be replaced without interrupting the flow of hydraulic fluid between the actuator and the servo valve.
still further object of the invention is to provide a method for protecting an end user mechanism or device such as a servo valve from contaminants in an operating fluid flowing from a source to the end user device, which method includes providing a dual filter isolation block between the operating fluid source and the end user device; providing a pair of fluid paths in the isolation block, both of which fluid paths include a removable filter; providing a pair of slidably-operated spools having areas of reduced diameter in the isolation block for intersecting the fluid paths, respectively; and operating the spools in concert to direct a flow of operating fluid from the fluid source through one of the fluid paths and its associated filter and spool in the isolation block, to the user device, thus facilitating removal and replacement of the second filter without interrupting the flow of operating fluid from the source to the user device.